Positive displacement internal combustion engines (ICEs) typically do not inject steam or water as part of the expansion (power) stroke, due to the fact that the timing of the mixing process to achieve a satisfactory or optimal mix is extremely difficult and requires costly hardware components. Indeed, it has been found that systems that have purported to inject water or steam into the combustion gas require extremely precise timing and have proven to be unreliable over time. Since current engine systems do not include water as part of the expansion cycle, no provision is made to reclaim it.
In some combined cycle engine systems which do incorporate water as part of the expansion process, such as water injection in gas turbines, it may not be necessary to reclaim the water, in which case it is simply expelled to the atmosphere. Examples where such systems may be installed include ground-based power production facilities, or aircraft which use water injection during take-off, but do not wish to carry the added weight of an on-board water supply during flight.
On the other hand, in some applications, it is necessary to provide an available water supply for use as an expansion fluid and reclamation to the extent possible. Examples of these applications include remote facilities where water is relatively scarce, or transportation systems where the range of travel is limited by the volume of on-board storage. In such circumstances, reclamation of a portion of the water used in the expansion process is desirable, so that the total or net utilization of water from storage may be reduced. Using a simple example for a vehicle application, if the flow rate of water through the system is five gallons per hour, then in six hours of travel at sixty miles per hour (a 360 mile range), the vehicle requires a thirty gallon water storage capacity. Employing a reclamation sub-system that is capable of reclaiming 50% of the expansion water would reduce the storage requirement for the same three-hundred, sixty mile range to fifteen gallons which, in a variety of applications, especially a vehicle, as in the present example, is economically beneficial for a number of reasons.
First of all, reducing the storage capacity required for the expansion fluid reduces the overall weight of the vehicle. A reduction of fifteen gallons of water saves one hundred twenty pounds of weight, which improves both vehicle performance and efficiency. Secondly, reducing the quantity of water required means that a smaller volume storage container can be used. A third issue is the matter of cost. If the water to be supplied to the engine must be filtered, then it would be highly desirable to save the cost of an additional fifteen gallons per fill-up.